The present invention relates to a method for gasifying carbonaceous fine-grained or sludgy material, such as powdered brown coal or biomass, within fixed bed reactors, wherein the carbonaceous material to be gasified is pre-heated and dried, especially prior to introduction into the fixed bed reactor, with the vapors resulting from the pre-heating and drying being admixed with the gasification medium, while the carbonaceous material to be gasified is mixed with coarse-grained ballast material either within or prior to introduction into the fixed bed reactor, to improve the gas permeability of the fine-grained or sludgy carbonaceous material.
It is known to burn and/or gasify carbonaceous material, e.g. within a gasification reactor. The gasification reactor must be charged with material of a given minimum granular size. Material having a smaller granular size will result in inadequate gasification, thus considerably reducing the effectiveness of a gasification plant. Moreover, the material to be gasified should have a minimum ash content, so that after passing through the gasification zone, there is adequate material for gas distribution as well as for gas heating.
For the above reasons, various kinds of dust, sawdust or sewage sludge can be gasified only to an extremely limited extent, and supplied for heat-economical use. Wash refuse, which is developed in coal mining, is similarly unsuitable for gasification, due to the low carbon content thereof, and is thus virtually suitable only as a deposit.
In order to counteract these disadvantages, powdery fuels are usually briquetted. The briquettes may be produced in a gas-permeable (tubular) shape (DE-OS No. 22 56 383). Alternatively, a gasification retort is charged alternately with fine-grained and coarse-grained material, in order to improve the gas permeability (DE-PS No. 168,873, AT-PS No. 64,423).